Electric submersible pump (ESP) power cables and motor lead extensions (MLE) incorporate high integrity insulation and armor. Conventional cables may rely on lead layers to resist high temperatures and pressures, and corrosives in the well fluid. While the lead sheaths provide excellent barrier properties, the regulation of lead metal and its use can results in leaded cables with reduced reliability and lower lifespan.
In conventional cable-making, lead metal is extruded onto the insulation in its own separate extrusion process. The insulation, however, has already been post-cured and does not bond very significantly with the molten lead. Due to this lack of interfacial bonding and a difference in the coefficient of thermal expansion between these materials, gas-filled micro-voids and impurities carried over from previous post-curing processes are introduced between the conventional insulation layer and the conventional lead sheath.
The dielectric constant within the unintended micro-voids and gaps is less than that of the surrounding dielectric, allowing the possibility of partial discharges—localized dielectric breakdowns of the insulation.
Gas-filled micro-voids or packets between the insulation and the conventional lead barrier may also cause barrier layer damage, such as lead barrier rupture during conditions when the cable is rapidly being depressurized or undergoing cyclic pressurization.